The Greddy BOV was one of my first mods, being that the stock BOV leaks by design, and that did not sit well with me.

I decided to stay with Greddy, who I had bought all my gauges from, and I could get there stuff at a local speed shop.

As soon as I worked up the courage to rip out all the intercooler pipes, battery and MAS, I installed it. (hey I was a noob at the time. that was alot of engine bay missing.)

I took the instructions off from stealth316, and installed it with Rob Becks adaptor kit. (with 6 speed re-pipe.)

Rob Becks adaptor kit worked awesome by the way, but that's besides the point.

The main point of this post is to say that the Greddy BOV leaked air out of the second nipple. To be exact, it sucked air in under idle (unmetered), and leaked it out (open loop) when operating. I am talking about the nipple coming out of the valve body, which is the smaller one. NOT the one coming out of the purple hat.

After reviewing with a Greg, who knows these cars better than me (especially at that time!) we decided it would be best to cap the nipple off.

So that is what I did.

After several "OMG n00b" calls later on 3si when I suggested to cap the nipple, I stopped advocating it online, as my advice was the opposite of stealth316, and no one does that, especially on 3si.

So, since I no longer need the BOV as I have moved onto a tial, and I'll throw the BOV off a bridge before I sell it for 25 bucks like the knock offs (which seems to be all people want now) I decided to disect it, and see once and for all: cap, or open to atmosphere.

The purple hat that has the first nipple sticking out of it goes into a rubber membrane, and when you let off the gas after a hard "into boost" run, the throttle plate slaps shut, creating vacuum in the plenum. this vacuum gets feed via a vacuum line to the first nipple in the BOV, thus, helping to create even more differencial pressure on either side of the valve. this helps the BOV to operate at the right time. Due to the rubber membrane, the vacuum/boost cannot escape from under the purple hat.

The second nipple feeds into the side of the valve body, which leads under the rubber membrane, and by the valve stem that pushes the face of the valve down to keep the boost on the boost side, and the vacuum on the vaccum side (pre-turbo).

By keeping this second nipple unplugged, you are leaving an open hole that feeds past the valve stem right into the splitter behind the MAS. Thus, anytime you get on the gas, unmetered air is being fed into your engine.

Also note that anytime you shift while in boost, you are letting boost out open loop, which completely defeats the purpose of the recirculation part of this BOV.

If you are running the BOV open loop on purpose, then the second nipple doesn't really matter. either way is open to atmosphere.

If you are running huge amounts of boost, greddy recomends that you run another plenum vacuum source to that second nipple. This now makes sense, as it's dumping right behind the valve face, which will again raise the difference in pressure between the two sides, and help the valve pop off at the appropriate time. However, this will cause a constant boost recirculation from after turbo to before turbo. So if you feel you need to do this, keep that in mind.

If you are running huge amounts of boost, greddy recomends that you run another plenum vacuum source to that second nipple. This now makes sense, as it's dumping right behind the valve face, which will again raise the difference in pressure between the two sides, and help the valve pop off at the appropriate time. However, this will cause a constant boost recirculation from after turbo to before turbo. So if you feel you need to do this, keep that in mind.

Actually!

I've found on our cars (with the STOCK cams and no boost leaks), you don't need to do that. You can set it to the firmest setting and still have it work properly. This is because our motors draw a lot of vaccum (19mmhg+).

Just add that retard to your ignore list. The guys head is so far up his a$$ he can't see for $hit. Check out the 5 or so threads about an issue his car is having. I tryed to help him in one of them...

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